全文获取类型
收费全文 | 10399篇 |
免费 | 761篇 |
国内免费 | 1379篇 |
专业分类
化学 | 3680篇 |
晶体学 | 52篇 |
力学 | 202篇 |
综合类 | 164篇 |
数学 | 6739篇 |
物理学 | 1702篇 |
出版年
2024年 | 7篇 |
2023年 | 104篇 |
2022年 | 132篇 |
2021年 | 253篇 |
2020年 | 251篇 |
2019年 | 303篇 |
2018年 | 293篇 |
2017年 | 314篇 |
2016年 | 237篇 |
2015年 | 227篇 |
2014年 | 380篇 |
2013年 | 1103篇 |
2012年 | 368篇 |
2011年 | 499篇 |
2010年 | 429篇 |
2009年 | 575篇 |
2008年 | 649篇 |
2007年 | 812篇 |
2006年 | 630篇 |
2005年 | 574篇 |
2004年 | 495篇 |
2003年 | 528篇 |
2002年 | 489篇 |
2001年 | 398篇 |
2000年 | 385篇 |
1999年 | 370篇 |
1998年 | 337篇 |
1997年 | 292篇 |
1996年 | 209篇 |
1995年 | 117篇 |
1994年 | 141篇 |
1993年 | 88篇 |
1992年 | 84篇 |
1991年 | 61篇 |
1990年 | 46篇 |
1989年 | 46篇 |
1988年 | 49篇 |
1987年 | 46篇 |
1986年 | 26篇 |
1985年 | 44篇 |
1984年 | 28篇 |
1983年 | 17篇 |
1982年 | 19篇 |
1981年 | 20篇 |
1980年 | 11篇 |
1979年 | 10篇 |
1978年 | 11篇 |
1977年 | 12篇 |
1976年 | 5篇 |
1973年 | 4篇 |
排序方式: 共有10000条查询结果,搜索用时 515 毫秒
101.
Salvador Hernández 《Topology and its Applications》2007,154(10):2089-2098
Let C(X,G) be the group of continuous functions from a topological space X into a topological group G with pointwise multiplication as the composition law, endowed with the uniform convergence topology. To what extent does the group structure of C(X,G) determine the topology of X? More generally, when does the existence of a group homomorphism H between the groups C(X,G) and C(Y,G) implies that there is a continuous map h of Y into X such that H is canonically represented by h? We prove that, for any topological group G and compact spaces X and Y, every non-vanishing C-isomorphism (defined below) H of C(X,G) into C(Y,G) is automatically continuous and can be canonically represented by a continuous map h of Y into X. Some applications to specific groups and examples are given in the paper. 相似文献
102.
We study the propagation of a quantum probe light in an ensemble of tripod level atoms when the atoms are coupled to two other classical control fields. First we calculate the dispersion properties, such as susceptibility and group velocity, of the probe light within such an atomic medium under the case of three-photon resonance via the dynamical algebra method of collective atomic excitations. Then we calculate the dispersion of the probe light in the case that two classical control fields have the different detunings to the relative atomic transitions. Our results show that in both cases the phenomenon of electromagnetically induced transparency can occur. Especially under the second case, we can find two transparency windows for the probe light. 相似文献
103.
John Ginsburg 《Order》1989,6(2):137-157
For a partially ordered setP and an elementx ofP, a subsetS ofP is called a cutset forx inP if every element ofS is noncomparable tox and every maximal chain ofP meets {x}∪S. We letc(P) denote the smallest integerk such that every elementx ofP has a cutsetS with ‖S‖?k: Ifc(P)?n we say thatP has then-cutset property. Our results bear on the following question: givenP, what is the smallestn such thatP can be embedded in a partially ordered set having then-cutset property? As usual, 2 n denotes the Boolean lattice of all subsets of ann-element set, andB n denotes the set of atoms and co-atoms of 2 n . We establish the following results: (i) a characterization, by means of forbidden configurations, of whichP can be embedded in a partially ordered set having the 1-cutset property; (ii) ifP contains a copy of 2 n , thenc(P)?2[n/2]?1; (iii) for everyn>3 there is a partially ordered setP containing 2 n such thatc(P)<c(2 n ); (iv) for every positive integern there is a positive integerN such that, ifB m is contained in a partially ordered set having then-cutset property, thenm?N. 相似文献
104.
In this paper, a characterization of almost periodicity of topological transformation groups on uniform spaces is given. By searching the appropriate base for uniform structure, it is shown that the topological transformation group is topologically equivalent to an isometric one if it is uniformly equicontinuous. 相似文献
105.
106.
Applied Biochemistry and Biotechnology - 相似文献
107.
108.
对股份制公司的综合投资方案的决策问题进行了研究.首先依据多个投资方案的风险与收益并存的实际情况,建立了最佳投资组合方案的多目标决策模型.然后,由董事会综合各股东所持股份和相互评价权值,利用群决策的方法得到一个最终投资方案,此方案在理论上能使公司获得最大收益. 相似文献
109.
He Ping LIU Xuan Yuan ZHENG 《数学学报(英文版)》2006,22(2):425-430
We consider the commutators of the HSrmander multiplier with CMO-functions on the Heisenberg group. The result of compactness on L^P spaces is proved. 相似文献
110.